So it looks like other application occupies SQL Server default instance port TCP 1433.
To find out what is using 1433, I ran netstat.exe as follows:

I found one process using TCP 1433 and its process ID was 5136 as you can see at the end of the output above.

And now I ran Process Explorer (procexp.exe) to check out which application it is. (Sure, you can run Task Manager or any other process monitoring utility) It turns out that PID 5136 was Google Chrome (surprisingly!) and it was connecting to Google owned 1e100.net server (173.194.33.146).

I killed Google Chrome and restarted SQL Server... and everything worked fine...